Field of the Invention
The present invention relates to a wind turbine blade vortex generator unit for a wind turbine blade, where said wind turbine blade comprises at least a root end, a distal tip end, a pressure side and a suction side, where said pressure side and said suction side constitute an aerodynamic profile with a leading edge and a trailing edge, hereinafter referred to as an airfoil, and where said wind turbine blade comprises at least one series of vortex generator units, comprising fins extending substantially perpendicular to the surface of said airfoil and substantially in a direction from the leading edge towards the trailing edge of the wind turbine blade, where said fins have a height measured perpendicular from a base having a width and a thickness and to a free end, where the vortex generator units each comprises a fin connected to an outer side of said base, and where said fin is tapered from a trailing edge side towards a leading edge side and thus appears delta shaped, and where each of said vortex generator units further comprises a layer of adhesive on an inner side of said base, extending in a base plane.
Description of Related Art
The present invention also relates to a method for installing a series of vortex generator units at a wind turbine blade, and even further to a wind turbine blade comprising such a vortex generator unit.
The development of more cost-effective wind turbines means that the size and height of wind turbines have an increasing role. The size of wind turbine blades has been increased over years and still is. Designing an effective blade becomes more and more difficult as the blades become longer and wider and because of the fact that the blades have to be optimized to quite a span in wind speeds and to other factors that might have influence on the performance of a specific aerodynamic profile. Therefore, there remains a need for improving the aerodynamic properties of wind turbine blades according to specific needs. Such needs will typically be calculated either theoretical or on behalf of specific measurements, but also measurements alone can be used as input for performing improvements.
Wind turbine blades typically comprise an airfoil shaped shell which is supported by using internal reinforcement structures. The airfoil shape and the internal structure of a wind turbine blade will typically be designed as effective as possible but still with an eye to as low energy cost (COE) as possible in a particular target market (wind range and environmental requirements).
The design of the airfoil shape of a wind turbine blade is thus a trade-off between power production, structural mass and cost, induced loads, noise and transport considerations. As a consequence of this, the efficiency of the blades are very often also a trade-off as it is costly to manufacture and time consuming to design and manufacture molds for each and every specific blade condition. Thus, blades are designed, molds are prepared and blades are manufactured in order to be as close to optimum as possible.
To obtain a closer to optimum solution, it is known to attach different devices, such as vortex generators, gurney flaps, and trailing edge extender in form of a tape, to the wind turbine blade, in order to make the trade-offs less problematic and thus make a specific blade design perform better under specific conditions.
Vortex generators, as well as gurney flaps, are used to optimize the aerodynamic performance, and a trailing edge extender made from tape will reduce noise generated from the blade. Such tape is so flexible that it has no capacity to redirect the air flow passing over the blade, and hence it has no impact on the lift coefficient of the blade profile.
From U.S. Patent Application Publication 2012/0257977 A1 a vortex generator comprising two fins is known where the base of the vortex generator comprises a recess for an adhesive pad to be mounted. This should apparently solve the problem from the prior art solutions of having to seal along the perimeter of the base. In order to allow the adhesive pad to be put in contact with the surface of a wind turbine blade, the recess is a little less deep than the thickness of the adhesive pad. This will evidently leave a narrow gap along the perimeter of the base.
International Patent Application WO 2007/140771 A1 and corresponding U.S. Pat. No. 8,678,746 disclose a strip having one or more vortex generators where the base of the strip has the same width at the leading and trailing edges of the projecting fin. This wide frontal edge of the base will disrupt the air flow in the boundary layers around the vortex generator, thereby reducing the effect of the vortex generator.